Magenta couplers represented by the following general formula (I) are known from, for example, JP-A No. 59-162548 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A No. 60-43659, JP-A No. 59-171956, JP-A No. 60-172982, and JP-A No. 60-33552, and U.S. Pat. No. 3,061,432, and various studies have been made thereon due to their excellent hues: ##STR3## wherein R.sub.11 represents a hydrogen atom or a substituent, X represents a hydrogen atom or a group capable of being eliminated by a coupling reaction with an oxidation product of an aromatic primary amine developing agent, Za, Zb, and Zc each represents a methine group, a substituted methine group, .dbd.N-- or --NH--, provided that one of the Za--Zb bond and the Zb--Zc bond is a double bond and the other is a single bond and, when Zb--Zc is a carbon-to-carbon double bond, it may be a part of an aromatic ring, and a dimer or higher polymer may be formed at R.sub.11 or X, or, when Za, Zb or Zc represents a substituted methine group, a dimer or higher polymer may be formed at the substituted methine group.
It has been found, however, that magenta couplers of general formula (I) have the defect that, when processed with a conventional color developer, they show poor color-forming properties, a serious variation in photographic properties and, after being processed, are liable to cause magenta stain with time.
As to variation of photographic properties, it has been found that variations in the concentration of sulfite ion (conventionally added to a color developer) have a serious influence. Therefore, various preservatives or chelating agents have been added to color developers to keep the above-described concentration of sulfite ion at a constant level in a stable fashion. However, effective techniques have not yet been discovered. It has then been found that when sulfite ion is eliminated, the concentrations of hydroxylamines or color-developing agents vary so much that there also results a detrimental influence on photographic properties. Therefore, preservatives for replacing sulfite ion are necessary. However, the addition of triethanolamines described in U.S. Pat. No. 4,170,478 and poly(ethyleneimines) described in U.S. Pat. No. 4,252,892 have failed to provide sufficient results.
On the other hand, as to formation of magenta stain caused after processing, conventional anti-fading techniques or stain-preventing techniques (anti-fading techniques include adding various compounds such as hydroquinone derivatives described in, for example, U.S. Pat. Nos. 2,360,290, 2,418,613, 2,675,314, 2,701,197, 2,704,713, 2,728,659, 2,732,300, 2,735,765, 2,710,801, and 2,816,028, British Pat. No. 1,363,921, and JP-A No. 58-24141, gallic acid derivatives described in U.S. Pat. Nos. 3,457,079 and 3,069,262, p-alkoxyphenols described in U.S. Pat. Nos. 2,735,765, and 3,698,909, JP-B No. 49-20977 (the term "JP-B" as used herein means an "examined Japanese patent publication") and JP-B No. 52-6623, p-hydroxyphenol derivatives described in U.S. Pat. Nos. 3,432,300, 3,573,050, 3,574,627 and 3,764,337, JP-A No. 52-35633, JP-A No. 52-147434 and JP-A No. 52-152225, and bisphenols described in U.S. Pat. No. 3,700,455; and the stain-preventing techniques described in, for example, JP-A No. 49-11330, JP-A No. 50-57223, JP-A No. 56-85747, and JP-B No. 56-8346) have failed to provide sufficient results.
As is described above, it has been desired to develop a technique of overcoming the defects of magenta couplers represented by general formula (I).